a wire with diameter 2.0 mm and length of 10 m is made of an unknown material. the wire has a resistance of 4.2 ohm. calculate the resistance of a wire with a 1.6 mm diameter and 20 m length made of the same material



Answer :

The resistance of a wire with a 1.6 mm diameter and 20 m length made of the same material is 3.14×10⁻⁷Ω−m.

What does "resistance" mean?

Electrical resistance of a conductor with a unit cross-sectional area and unit length is called resistivity. Resistivity is a distinctive attribute of any material that may be used to compare different materials based on how well they conduct electric currents. Low conductivity is indicated by high resistance.

Given,

l= 10m= 1000mm

d= 2mm

∴radius(r)= 20.2 =0.1mm

R=10Ω

To find,

Resistivity(ρ)

ρ=R /l A

​where,

R= Resistance

l= Length of wire

A= Cross sectional area of wire

Cross sectional area of cylinder (A)=Πr²

A= π×(0.1)²

A=0.0314mm²

ρ=10(10000.0341)

ρ=0.000314Ω−mm

ρ≃3.14×10⁻⁷Ω−m

So, the resistivity of the material is equal to 3.14×10⁻⁷Ω−m.

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